[APD] LEDs and color temperature

[Andrew McLeod <thefish at theabyssalplain_freeserve.co.uk>]

On Sat, 3 Jan 2004 18:14:35 -0500, Ivo Busko <busko at stsci_edu> wrote:

> "S. Hieber" <shieber at yahoo_com> wrote:
> <snip>
> > plants? I'd like to hear about that lamp, energy
> > efficiency, light dispersion, spectral output, etc.
>
> Long time ago I posted something about LEDs (see
> http://fins.actwin.com/aquaticplants/month.200108/msg00601.htm
> l)
>
> As far as I can tell, LEDs are not more efficient than
> regular incandescent bulbs. And won't become better than
> fluorescents are nowadays (about 30% efficiency). IMHO,
> not good enough to justify the expense.
That link didn't work for me, but I have another one (that probably won't 
work soon?).

http://physicsweb.org/article/news/6/5/9

I'm not suggesting the 'organic LED's' of the article are worth waiting 
for, but there was some interesting information. Specifically, it said 
that normal (non-white) LED's produced light at only one wavelength. I 
assume, it would therefore be expensive to make a white LED, and so it 
would be better to use a large array of primarily red and blue LED's whose 
wavelengths are in the absorbtion range of photosynthesis (does 
photosynthesis occur over a wide range or a few discrete wavelengths?). 
I'm not sure if the plants would appear well 'illuminated' if you just 
used red and blue, though, because there would be no green light for you 
to see them by! (Incidentally the organic LED described would be an 
excellent all-round light source as it would produce a wide spectrum like 
an incandescent but be more efficient?)

This link has a comparison of lumen/watt efficiency.
http://www.otherpower.com/otherpower_lighting.html
It also states that LED's are a horrendously inefficient way to light 
larger objects (although it also says a 100W light bulb would still be 
marginally less efficient than LED's?).

--
Happy Self-Confessed Armchair Aquarist (until I get my own room), Andrew 
McLeod
thefish at theabyssalplain_freeserve.co.uk
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